I have spoken in several recent articles about antennas that exhibit a simple series resonance with constant or near constant R near resonance.
Sometimes the impedance transformation used may hide that simplicity. Continue reading Simple resonators might not appear as such initially
This article explores a generic VSWR curve for simple series resonant matched antennas. Continue reading VSWR curve of a simple series resonant antenna
Off centre fed (OCF) dipoles are very popular with Hams on HF.
Many claims are made for variations of the theme, but the essential common feature is that the offset feed point provides a feed point impedance that is not too unsuited to 50Ω coaxial feed line at the fundamental resonance of the dipole and half wave harmonics. Continue reading OCF dipoles
There is a common Rule of Thumb that to be effective, the magnitude of common mode impedance of a Guanella current balun in an antenna system should be at least 500Ω (Reisert 1978).
This article proposes a possible origin for this thinking, and discusses the validity of the underlying model. Continue reading Baluns – Rule 500
I am often asked for recommendations for a replacement for TLLC (Duffy 2001).
The announcement of an update to TLW by ARRL / N6BV in June 2014 QST flagged a possibility.
Reviewing the available cable types, Belded 8215 (RG-6/U type) was tested for loss with a 75+j0Ω load (approximately a matched load) at 1MHz, and the result of1.147dB does not reconcile with the Belden datasheet showing 1.3124dB, an error of -13%. Continue reading TLW v3.24 checkout
One sees simplistic application of ohms law to antenna balun problems frequently in online forums, but is the technique valid? Continue reading Using Ohms law on antenna baluns
At (Bertelsmeier & Magnin 1992) formulas are given for calculating G/T from Sun/ColdSky Y factor in several Ham bands, and solar flux at 10.7cm. Continue reading DJ9BV & F6HYE G/T formula
For those who may have used or want to use my G/T spreadsheet tool I have discovered a defect in one cell’s formula. Continue reading G/T spreadsheet update (v1.09)
VE7BQH publishes a table of Yagi performance data derived from a number of modelling programmes. The table is often used as a definitive reference of the overall merit of an antenna by buyers, makers and students for their own situation.
This article is mainly motivated at better understanding the G/T column of the tables. Continue reading Trying to make sense of the VE7BQH Yagi performance tables
Folk often ask for instructions for assembly of so-called clamp type coax connectors.
This article shows such an N type connector, but the techniques are applicable to different connectors with the same type of cable / braid attachment. Continue reading Assembling clamp type coax connectors